Pipe provided with corrosion prevention layer on the outside surface, process for production of the same, and process for production of alloy wires used for the corrosion prevention layer

ABSTRACT

Disclosed is a pipe made of an iron-base material, having a corrosion prevention layer formed on the surface thereof. The corrosion prevention layer includes a Zn—Sn sprayed coating including Sn in a content of more than 1% by mass and less than 50% by mass and the balance composed of Zn. Alternatively, the corrosion prevention layer includes a Zn—Sn—Mg sprayed coating including Sn in a content of more than 1% by mass and less than 50% by mass, Mg in a content of more than 0.01% by mass and less than 5% by mass and the balance composed of Zn. Preferably, the sprayed coating of the corrosion prevention layer includes at least any one of Ti, Co, Ni and P, and the content of each of these elements is more than 0.001% by mass and less than 3% by mass.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/733,569, filed Mar. 9, 2010, which is a U.S. National StageApplication of International Application No. PCT/JP09/01193, filed Mar.18, 2009, which claims priority from Japanese Patent Application No.2008-074781, filed Mar. 24, 2008 and Japanese Patent Application No.2008-136141, filed May 26, 2008; said patent applications hereby fullyincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a pipe provided with a corrosionprevention layer on the outside surface thereof, a process forproduction of the pipe and a process for production of alloy wires usedfor the corrosion prevention layer, in particular, a pipe provided witha corrosion prevention layer on the outside surface thereof wherein thecorrosion prevention layer is formed with a metal sprayed coating on thesurface of the pipe made of an iron-base material, such as a cast-ironpipe, a process for production of the pipe, and a process for productionof alloy wires to be used for the corrosion prevention layer.

BACKGROUND ART

Metal pipes practically used as laid underground have been provided withtar or bitumen coating since long ago for the purpose of corrosionprevention. When the coating of a metal pipe is scratched, however, thecorrosion of the metal pipe progresses from the scratched portions. Forthe purpose of solving such a corrosion problem, the following corrosionprevention is widely applied: a metal coating having a higher ionizationtendency than the ionization tendency of the material of a metal pipe isformed on the surface of the metal pipe, the metal coating undergoes thegeneration of a sacrificial anode function due to the ionizationtendency difference, and thus the metal coating prevents the corrosionstarting from the scratched portions. Zinc is a typical metal havingsuch a sacrificial anode function. A zinc coating is formed on thesurface of a metal pipe such as an iron pipe by plating or spraying.Such a coating is used, as it is, as the outermost surface layer, or asit is further overcoated with another layer. Zinc has a high ionizationtendency; the electrochemical potential difference between iron and zincis large, and accordingly, in a case where zinc is used in combinationwith an iron-base metal, even when some scratches are caused in thecoating, the sacrificial anode function is displayed and the corrosionin the scratched portions can be suppressed. In the case of cast-ironpipes widely used as water and sewage pipelines, the coating is coveredwith a polyethylene sheet referred to as a polyethylene sleeve to blockthe coating from the external environment, and consequently thecorrosion prevention effect is further enhanced.

However, zinc has a high ionization tendency, and hence zinc hardlymaintains the sacrificial anode function over a long period of time. Asa solution to solve this problem, the increase of the zinc coatingamount is an effective technique. However, in this case, in addition tothe increase of the material cost, the work time is increased and theproduction efficiency is also degraded.

Alternatively, as another method, a zinc-aluminum alloy is used(WO94/19640) as the case may be. The addition of aluminum alleviates theionization, and consequently the retention time of the sacrificial anodeeffect is maintained over a longer period of time.

However, as for aluminum, health concern is raised from some viewpoints,and the safety of aluminum as a material applied to drink water supplypipes is not established. For example, in a pipe joint having aninserting-receiving structure in which the inside of a socket formed atone end of a pipe receives a spigot formed at one end of another pipe,the outer surface of the spigot is brought into contact with tap water,thus causing a possibility that aluminum is eluted from the outersurface of the spigot.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a solution enabling tosolve the above-described technical problems without drasticallyincreasing the coating amount or without using aluminum.

Means for Solving the Problems

For the purpose of achieving the above-described object, the pipeprovided with a corrosion prevention layer on the outside surfacethereof, of the present invention, is a pipe wherein: the corrosionprevention layer is formed on the surface of the pipe made of aniron-base material; and the corrosion prevention layer includes eitherone of a Zn—Sn alloy sprayed coating including Sn in a content of morethan 1% by mass and less than 50% by mass and the balance composed of Znand a Zn—Sn—Mg alloy sprayed coating including Sn in a content of morethan 1% by mass and less than 50% by mass, Mg in a content of more than0.01% by mass and less than 5% by mass and the balance composed of Zn.

The alloy sprayed coating of the corrosion prevention layer of the pipeprovided with a corrosion prevention layer on the outside surfacethereof of the present invention, preferably includes at least any oneof Ti, Co, Ni and P, and the content of each of Ti, Co, Ni and P is morethan 0.001% by mass and less than 3% by mass.

A process for production of a pipe provided with a corrosion preventionlayer on the outside surface thereof of the present invention includes,when the pipe provided with a corrosion prevention layer on the outsidesurface thereof is produced, heat treating the alloy sprayed coating ata temperature equal to or higher than the eutectic temperature of thealloy and lower than the melting point of the alloy.

Another process for production of a pipe provided with a corrosionprevention layer on the outside surface thereof of the present inventionincludes, when the pipe provided with a corrosion prevention layer onthe outside surface thereof is produced, using one of a Zn—Sn wire, aZn—Sn—Mg wire and a wire produced by including at least any one of Ti,Co, Ni and P in one of a Zn—Sn wire and a Zn—Sn—Mg wire as a first wireand a Zn wire as a second wire; and simultaneously arc spraying thefirst wire and the second wire.

A process for production of an alloy wire of the present inventionincludes: melting a material including Sn in a content of more than 1%by mass and less than 50% by mass, Mg in a content of more than 0.01% bymass and less than 5% by mass and the balance composed of Zn; andcooling the molten alloy under solidification, obtained by the melting,at a cooling rate of 20° C./sec or more from a temperature equal to andhigher than the eutectic temperature of the Zn—Sn—Mg alloy down to atemperature of 50° C. or lower while the molten alloy is beingsolidified so as to yield a wire rod type cast product with a continuouscasting machine.

According to the process for production of an alloy wire of the presentinvention, cooling water is preferably sprayed onto the molten alloyunder solidification so as to yield a wire rod type cast product.

Advantages of the Invention

According to the pipe provided with a corrosion prevention layer on theoutside surface thereof of the present invention, the corrosionprevention layer on the outside surface of a pipe made of an iron-basematerial includes a Zn—Sn alloy sprayed coating or a Zn—Sn—Mg alloysprayed coating, and hence the corrosion prevention performance can bedrastically improved as compared to a pipe using a simple zinc sprayedcoating; additionally, Al is not used and hence no problems associatedwith health are caused. Moreover, Sn, which is soft, is used, and hencethe Zn—Sn alloy or the Zn—Sn—Mg alloy can be easily worked into a Zn—Snwire or a Zn—Sn—Mg wire, respectively, and consequently a spray materialcan be formed without any problem.

According to the present invention, the alloy sprayed coating includesat least any one of Ti, Co, Ni and P in a predetermined content, andhence the corrosion prevention performance can be more improved.

According to the present invention, the alloy sprayed coating is heattreated at a temperature equal to or higher than the eutectictemperature of the alloy and lower than the melting point of the alloy,and hence the corrosion prevention performance can be more improved.

According to the present invention, one of a Zn—Sn wire, a Zn—Sn—Mg wireand a wire produced by including at least any one of Ti, Co, Ni and P inone of a Zn—Sn wire and a Zn—Sn—Mg wire is used as a first wire and a Znwire is used as a second wire, and simultaneously the first wire and thesecond wire are arc sprayed, and hence the corrosion preventionperformance can be furthermore improved.

According to the present invention, a molten Zn—Sn—Mg alloy undersolidification is quenched from a temperature equal to or higher thanthe eutectic temperature of the Zn—Sn—Mg alloy down to a temperature of50° C. or lower while the molten alloy is being solidified so as toyield a wire rod type cast product with a continuous casting machine,and hence the zinc crystals can be refined, and accordingly themechanical properties of the alloy wire can be improved. Thus, aZn—Sn—Mg alloy wire to be hardly broken in a wiredrawing step can beproduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a production apparatus used for a processof production of an alloy wire of the present invention;

FIG. 2 is a view illustrating a bending test method based on the presentinvention;

FIG. 3 is a view showing a result of an optical microscope observationof the microstructure of a specimen produced under the conditionswithout water cooling; and

FIG. 4 is a view showing a result of an optical microscope observationof the microstructure of a specimen produced under the conditions withwater cooling.

BEST MODE FOR CARRYING OUT THE INVENTION

The pipe provided with a corrosion prevention layer on the outsidesurface thereof of the present invention is a pipe in which a corrosionprevention layer including an alloy sprayed coating is formed on thesurface of a pipe made of an iron-base material, such as a cast-ironpipe.

In a first aspect of the present invention, the alloy sprayed coating isformed with a Zn—Sn alloy sprayed coating including Sn in a content ofmore than 1% by mass and less than 50% by mass and the balance composedof Zn. By adopting an alloy sprayed coating formed by adding Sn topredominant Zn, the corrosion prevention performance can be improved ascompared to a sprayed coating using only Zn. The corrosion preventionperformance of the Zn—Sn alloy sprayed coating can be made approximatelythe same as the corrosion prevention performance of Zn-15Al (Zn: 85% bymass, Al: 15% by mass). When the content of Sn is 1% by mass or less, orwhen the content of Sn is 50% by mass or more, no substantialimprovement effect of the corrosion prevention performance due to theaddition of Sn can be obtained.

The inclusion of Sn also provides an advantage that white rust, namely,a corrosion product of Zn hardly occurs. In the case where white rusttends to occur, when a product having a black paint coating applied ontoa sprayed coating is stored outdoors and white rust is generated in theblack paint coating portion, such white rust shows up so clearly toresult in a problem that recoating is necessary at the time of shipping.

The inclusion of Sn, which is a soft material, also provides anadvantage that the production of the Zn—Sn alloy wire as a material forspraying is facilitated. Additionally, such a Zn—Sn alloy includes onlyZn and Sn, and hence causes no problem associated with health.

In a second aspect of the present invention, the alloy sprayed coatingis formed with a Zn—Sn—Mg alloy sprayed coating including Sn in acontent of more than 1% by mass and less than 50% by mass, Mg in acontent of more than 0.01% by mass and less than 5% by mass and thebalance composed of Zn.

Also in this case, as compared to a sprayed coating using only Zn, thecorrosion prevention performance can be improved. The corrosionprevention performance of the Zn—Sn—Mg alloy sprayed coating can be madeapproximately the same as or higher than the corrosion preventionperformance of Zn-15Al (Zn: 85% by mass, Al: 15% by mass).

When the content of Sn is 1% by mass or less and/or when the content ofMg is 0.01% by mass or less, no substantial improvement effect of thecorrosion prevention performance due to the addition of Sn and Mg can beobtained. On the other hand, also when the content of Sn is 50% by massor more and/or when the content of Mg is 5% by mass or more, similarlyno substantial improvement effect of the corrosion preventionperformance due to the addition of Sn and Mg can be obtained.

In the same manner as in the formation of the Zn—Sn alloy sprayedcoating, the formation of the Zn—Sn—Mg alloy sprayed coating alsoprovides the advantages that white rust hardly occurs, wires are easilyproduced and no problem associated with health occurs.

In the alloy sprayed coatings of the first and second aspects of thepresent invention, at least any one of Ti, Co, Ni and P can be included;in other words, any one, or any two to four, in combination, of theseelements can be included. The content of each of these elements ispreferably 0.001% by mass or more and 3% by mass or less. The inclusionof these elements in addition to Sn or Sn—Mg correspondingly reduces theamount of Zn.

The inclusion of these elements enables to further improve the corrosionprevention performance. However, when the content of each of theseelements is less than 0.001% by mass, no substantial improvement effectof the corrosion prevention performance due to the addition of theseelements can be obtained. On the other hand, also when the content ofeach of these elements is more than 3% by mass, no substantialimprovement effect of the corrosion prevention performance due to theaddition of these elements can be obtained.

In the same manner as described above, the inclusion of these elementsprovides the advantages that white rust hardly occurs, and because ofthe small contents of these elements, alloy wires can be producedwithout problems and no problem associated with health occurs.

The pipe provided with a corrosion prevention layer on the outsidesurface thereof of the present invention is a pipe in which thecorrosion prevention layer includes the above-described alloy sprayedcoating. The corrosion prevention layer is particularly preferably suchthat in addition to the alloy sprayed layer, another coating such as anovercoating is laminated on the alloy sprayed coating. The overcoatingcan be performed with an acrylic resin coating material or an epoxyresin coating material.

Next, description is made on the process for production of a pipeprovided with a corrosion prevention layer on the outside surfacethereof of the present invention, namely, the process for formation ofan alloy sprayed coating. Examples of the process for formation of analloy sprayed coating on the surface of a cast-iron pipe may include aknown spraying method, namely, a method in which a Zn—Sn wire, aZn—Sn—Mg wire or a wire produced by adding at least any one of Ti, Co,Ni and P to one of these wires is used and an arc spraying is applied.Alternatively, a spraying with an alloy powder, instead of a wire, canalso be adopted.

As an alternative to the above description, the Zn—Sn alloy sprayedcoating is also able to be obtained by a technique in which a Zn—Sn wireor a wire produced by adding to this wire at least any one of Ti, Co, Niand P is used as a first wire and a Zn wire is used as a second wire,and simultaneously the first wire and the second wire are arc sprayed.Similarly, the Zn—Sn—Mg alloy sprayed coating is also able to beobtained by a technique in which a Zn—Sn—Mg wire or a wire produced byadding to this wire at least any one of Ti, Co, Ni and P is used as afirst wire and a Zn wire is used as a second wire, and simultaneouslythe first wire and the second wire are arc sprayed.

For example, for the purpose of obtaining a Zn-25Sn-0.5Mg (Sn: 25% bymass, Mg: 0.5% by mass, Zn: the balance; hereinafter, similarrepresentations are adopted, as the case may be) alloy sprayed coating,instead of performing a simultaneous arc spraying by using two stringsof a Zn-25Sn-0.5Mg wire, a simultaneous arc spraying by using aZn-50Sn-1.0Mg wire and a Zn wire in equal amounts can also be performed.

In this way, the corrosion prevention performance can be furtherimproved. On the other hand, the use amount of the Zn—Sn—Mg wire can behalved, and hence the cost required for the preparation of the wire canbe reduced.

The reason for the fact that the adoption of such a spray method furtherimproves the corrosion prevention performance is not clear, but can beprobably attributed to each of or a synergetic effect of the following(a), (b) and (c).

(a) For example, when the simultaneous arc spraying is performed byusing the Zn—Sn—Mg alloy wire and the Zn wire, the Zn—Sn—Mg alloy and Znare both distributed in the sprayed coating thus formed. In this case,the Zn—Sn—Mg alloy is lower in electric potential than Zn, and when theZn—Sn—Mg alloy and Zn each function as a sacrificial anode, the Zn—Sn—Mgalloy preferentially begins to be eluted. The thus eluted Zn—Sn—Mg alloyforms another relatively stable coating on the surface of the coating,this stable coating probably suppresses the consumption or elution ofthe rest of the Zn—Sn—Mg alloy and Zn, and thus the corrosion preventionperformance is probably further improved.

(b) The presence of Zn in the coating offers a physical hindrance tosuppress the elution of the Zn—Sn—Mg alloy, alternatively in the casewhere the Zn—Sn—Mg alloy is eluted, the corrosion product of theZn—Sn—Mg alloy suppresses the elution of Zn, and thus the corrosionprevention performance is probably further improved.

(c) According to the observation of the present inventors, the porosityof a Zn-25Sn-0.5Mg sprayed coating obtained by using two stirrings of aZn-25Sn-0.5Mg wire was found to be about 15%; on the other hand, theporosity of another Zn-25Sn-0.5Mg sprayed coating obtained by using aZn-50Sn-1.0Mg wire and the Zn wire in equal amounts was found to beabout 12%. In other words, from the lower porosity of the lattercoating, the corrosion prevention performance is probably improved inthe latter coating. The lower porosity may be attributed to the effectof the use of the wires different in hardness from each other on thebasis of the fact that the Zn-50Sn-1.0Mg wire is softer than the Znwire.

In the production of the pipe provided with a corrosion prevention layeron the outside surface thereof of the present invention, preferably analloy sprayed coating is formed on a cast-iron pipe, and then the alloysprayed coating is heat treated at a temperature equal to or higher thanthe eutectic temperature (198° C.) of the alloy and lower than themelting point of the alloy. The application of such a heat treatmentenables to further improve the corrosion prevention performance. This ispresumably because only Sn is melted by the heat treatment at atemperature higher than the eutectic temperature of the Zn—Sn alloy orthe Zn—Sn—Mg alloy, thus the fine voids having been created in thesprayed coating are filled with the molten Sn, and consequently acast-iron pipe provided with such a coating is capable of suppressingthe penetration of electrolytes into the coating when the cast-iron pipeis laid underground.

Accordingly, a heat treatment at a temperature lower than the eutectictemperature substantially does not melt Sn, and hence theabove-described effect is not able to be obtained. On the other hand,the heat treatment temperature is higher than the melting point of thealloy sprayed coating, the oxidation of the alloy is made to progressand the intrinsic corrosion prevention performance is lost.

The heat treatment time is not particularly limited; however, the heattreatment time is preferably 1 second to 60 minutes. When the heattreatment time is shorter than this range, the treatment time isinsufficient and no necessary heat treatment can be performed.

When the above-described overcoating is performed, the overcoating isperformed after the alloy sprayed coating is formed.

Hereinafter, the process for production of the Zn—Sn—Mg alloy wire isdescribed.

Various processes for production of alloy wires for use in metal sprayhave been known. However, any common production processes include awiredrawing step in which a wire having a predetermined cross-sectionalshape is drawn to be worked into an alloy wire having a predeterminedwire diameter. In other words, a working step of reducing the diameterof a wire is included. In this case, when the material for the wire islow in strength or ductility, wire breakage may occur. For the purposeof coping with such breakage, a treatment such as a heat treatment maybe performed depending on the material for the wire. In particular, inthe case of the Zn—Sn—Mg alloy wire, when the content of Sn is small,the wire is somewhat brittle, accordingly the workability is degradedand hence the wire breakage may occur in the wiredrawing step asdescribed above.

The process for production of the Zn—Sn—Mg alloy wire of the presentinvention is a production process which hardly causes wire breakage inthe wiredrawing step.

This production process, as described above, includes: melting amaterial including Sn in a content of more than 1% by mass and less than50% by mass, Mg in a content of more than 0.01% by mass and less than 5%by mass and the balance composed of Zn; and cooling the molten alloyunder solidification, obtained by the melting, at a cooling rate of 20°C./sec or more from a temperature equal to or higher than the eutectictemperature of the Zn—Sn—Mg alloy down to a temperature of 50° C. orlower while the molten alloy is being solidified so as to yield a wirerod type cast product with a continuous casting machine. In this way,the zinc crystals can be refined to improve the mechanical properties ofthe alloy wire. Consequently, a Zn—Sn—Mg alloy wire which is hardlybroken in the wiredrawing step can be produced.

The details of this production process are described. FIG. 1 illustratesthe configuration of a production apparatus for embodying thisproduction process. This apparatus includes a continuous casting machine101 and a take-up unit 102. In the casting machine 101, a groove 112having a U-shaped cross-section is formed on the circumference of therotary casting wheel 111. A crucible 115 is disposed above the castingwheel 111. The crucible 115 is capable of storing the molten alloy 103of the Zn—Sn—Mg alloy in the interior thereof and a molten alloy outlet116 is formed at the bottom of the crucible 115. In the vicinity of thecrucible 115, a spray nozzle 113 is disposed, and the spray nozzle 113is equipped with a spout 114 for spraying cooling water.

In the production, while the casting wheel 111 is being rotated slowly,the molten alloy 103 is fed to the portion of the groove 112 whichportion is located on the top of the casting wheel 111, from thecrucible 115. Then, the molten alloy 103 begins to be solidified due tothe heat removal by the casting wheel 111. Immediately after the startof the solidification, cooling water is sprayed from the spray nozzle113 onto the molten alloy 104 under solidification inside the groove112.

In this way, the molten alloy 104 under solidification is quenched toproduce an alloy wire 105. The alloy wire 105 is formed by the quenchingof the molten alloy 104 under solidification, hence the crystals arerefined and consequently the ductility of the alloy wire 105 can beimproved. The obtained alloy wire 105 is taken up by the take-up unit102.

The quenching by spraying cooling water from the spray nozzle 113 ontothe molten alloy under solidification 104 is preferably conducted asimmediately as possible after the casting of the molten alloy 103 intothe groove 112. For the purpose of attaining the improvement of theductility due to the crystal refining, it is required to adopt thecooling conditions that the cooling is performed at a cooling rate of20° C./sec or more from a temperature equal to or higher than theeutectic temperature of the Zn—Sn—Mg alloy, namely, 198° C., down to atemperature of 50° C. or lower.

In addition to the above-described water cooling, as long as a coolingtechnique can adopt the above-described cooling conditions, the coolingtechnique may be an air cooing using cold air, or alternatively acooling using another fluid.

The alloy wire 105 taken up by the take-up unit 102 is subsequentlysubjected to the wiredrawing step.

EXAMPLES

Hereinafter, Examples of the present invention are described. It is tobe noted that in following Examples, Comparative Examples, theevaluations of various physical properties were performed as follows.

(1) Workability into Wire

An alloy ingot of 47 mm in diameter X 350 mm in length was prepared andthe workability into wire was evaluated by measuring the Vickershardness. The alloy ingot after the hardness measurement was forged soas to have a reduced diameter of 10 mm and further wiredrawn so as tohave a diameter of 1.6 mm, and thus the workability was evaluated on thebasis of the following standards.

G (Good): Wiredrawing can be performed to a diameter of 1.6 mm.

P (Poor): Breakage occurs during wiredrawing.

(2) Corrosion Resistance

A corrosion resistance test was performed in the following manner.Specifically, a 150 mm×70 mm×2 mm sand-blast steel plate was used as aspecimen. On this plate, a 20 to 30-μm thick sprayed coating was formedat a spray amount of 130 g/m² by an electric arc spray technique using awire having a diameter of 1.6 mm, and thus a test sample was prepared.The corrosion resistance test and the evaluation method are as follows.

(2-1)

The salt spray test specified in JIS Z2371 was performed. In each of thecase where only the Zn—Sn alloy was sprayed and no heat treatment wasapplied and the case where only the Zn—Sn—Mg alloy was sprayed and noheat treatment was applied, the corrosion resistance was evaluated onthe basis of the degree of white rust occurrence and the time perioduntil red rust occurred. The degree of white rust occurrence wasvisually evaluated on the basis of the following standards.

G (Good): The degree of white rust occurrence is low.

A (Average): The degree of white rust occurrence is moderate.

P (Poor): The degree of white rust occurrence is high.

(2-2)

With respect to red rust, the evaluation was performed as follows. Inthe salt spray test for the case where only Zn was sprayed and no heattreatment was applied, the time period until red rust occurred wasdefined as “1”. With reference to this definition, in each of the casewhere only the Zn—Sn alloy was sprayed and the case where only theZn—Sn—Mg alloy was sprayed, the time period until red rust occurred inthe salt spray test was numerically evaluated for a test sample to whichno heat treatment was applied.

(2-3)

The time period until red rust occurred in the salt spray test wasevaluated for the case where any one of Ti, Co, Ni and P was singlyadded and no heat treatment was applied. Specifically, in each of theZn—Sn alloy free from the addition of these elements and the Zn—Sn—Mgalloy free from the addition of these elements, the time period untilred rust occurred without application of a heat treatment was defined as“1”; with reference to this definition, the time period concerned wasevaluated on the basis of the following standards.

E (Excellent): The time period until red rust occurred was longer by afactor of 1.5 or more.

G (Good): The time period until red rust occurred was longer by a factorof 1.0 or more and less than 1.5.

A (Average): The time period until red rust occurred was approximately1.

(2-4)

The time period until red rust occurred in the salt spray test wasevaluated for each of the case where only the Zn—Sn alloy was sprayedwithout adding Ti, Co, Ni and P and a heat treatment was applied and thecase where only the Zn—Sn—Mg alloy was sprayed without adding Ti, Co, Niand P and a heat treatment was applied. Specifically, for each of thetest samples subjected to a heat treatment for 30 minutes, measurementwas made on the heat treatment temperature range in which the timeperiod until red rust occurred was made longer and the corrosionprevention effect was able to be evaluated as improved as compared tothe corresponding case where no heat treatment was applied.

(2-5)

While a test sample free from the addition of Ti, Co, Ni and P and freefrom any heat treatment was being immersed in tap water at 30° C., thetime period until red rust occurred was evaluated. Specifically, thetime period until red rust occurred in a case where only Zn was sprayedwas defined as “1”; for the test sample, with reference to thisdefinition, the time period until red rust occurred was numericallyevaluated.

(2-6)

While a test sample free from the addition of Ti, Co, Ni and P and freefrom any heat treatment was being immersed in sulfuric acid of pH 3 at30° C., the time period until red rust occurred was evaluated.Specifically, the time period until red rust occurred in a case whereonly Zn was sprayed was defined as “1”; for the test sample, withreference to this definition, the time period until red rust occurredwas numerically evaluated.

Details of Examples and Comparative Examples are as follows.

Examples 1 to 6 and Comparative Examples 1 to 4

The Zn—Sn alloys having the component compositions shown in Table 1 weresprayed to prepare the test samples of Examples 1 to 6 and ComparativeExamples 1 to 4. The evaluation results of these test samples are shownin Table 1. In Comparative Examples 3, only Zn was sprayed and inComparative Example 4, only Sn was sprayed.

TABLE 1 Salt Spray Evaluation of the time period until red rust occurredHeat Immersion Immersion treatment in tap in sulfuric temperature wateracid Time range Time Time period in which the period period Degree ofuntil Addition amounts of corrosion until red until red white rust redrust Ti, Co, Ni and P prevention rust rust Components Hard- Workabilityoccurrence occurred (% by mass) effect was occurred occurred (% by mass)ness into [no heat [no heat [no heat treatment] improved [no heat [noheat Zn Sn Mg (Hv) wire treatment] treatment] 0.001 0.01 0.1 1 3 (° C.)treatment] treatment] Ex. 1 Balance 2 — 30 G G 10 A G E G A 198-410 1010-12 Ex. 2 Balance 10 — 30 G G 10 A G E G A 198-390 10 10-12 Ex. 3Balance 20 — 30 G G 10-12 A G G G A 198-380 10-12 10-12 Ex. 4 Balance 30— 30 G G 10-12 A G G G A 198-370 10-12 10-12 Ex. 5 Balance 40 — 30 G G10 A G E G A 198-350 10 10-12 Ex. 6 Balance 48 — 30 G G 10 A G E G A198-340 10 10-12 Com. Ex. 1 Balance 1 — 35 G A 2-3 A G E G A 198-410 2-32-3 Com. Ex. 2 Balance 50 — 25 G G 7-8 A G E G A 198-340 7-8 7-8 Com.Ex. 3 100 — — 35 G P 1 — — — — — — 1 1 Com. Ex. 4 — 100 — 10 G G <1 — —— — — — <1 <1

In Examples 1 to 6 and Comparative Examples 1 to 4, when Ti, Co, Ni andP were added and the salt spray test was performed, in any of the casesin which any one of Ti, Co, Ni and P was singly added, the sameevaluation results were obtained, by varying the addition amount, on thetime periods until red rust occurred. Therefore, in Table 1, forsimplicity, only one typical example is shown for each of Examples andComparative Examples. Specifically, Table 1 means that in each ofExamples 1 to 6 and Comparative Examples 1 to 4, for any one of Ti, Co,Ni and P, when the addition amount thereof was varied as 0.001, 0.01,0.1, 1 and 3% by mass, the same evaluation results were obtained for allthese elements.

Examples 7 to 42 and Comparative Examples 5 to 18

The Zn—Sn—Mg alloys having the component compositions shown in Table 2and Table 3 were sprayed onto the specimens to yield the test samples ofExamples 7 to 42 and Comparative Examples 5 to 14. The evaluationresults of the test samples of Examples 7 to 30 are shown in Table 2,and the evaluation results of the test samples of Examples 31 to 42 andComparative Examples 5 to 18 are shown in Table 3. For reference, ineach of Table 2 and Table 3, Comparative Examples 3 and 4 are againlisted.

TABLE 2 Salt Spray Evaluation of the time period until red rust occurredHeat Immersion Immersion treatment in tap in sulfuric temperature wateracid Time range Time Time period in which the period period Degree ofuntil Addition amounts of corrosion until red until red white rust redrust Ti, Co, Ni and P prevention rust rust Components Hard- Workabilityoccurrence occurred (% by mass) effect was occurred occurred (% by mass)ness into [no heat [no heat [no heat treatment] improved [no heat [noheat Zn Sn Mg (Hv) wire treatment] treatment] 0.001 0.01 0.1 1 3 (° C.)treatment] treatment] Ex. 7 Balance 2 0.02 35 G G 10-12 A G G G A198-410 10-12 10-12 Ex. 8 Balance 2 0.05 35 G G 10-12 A G G G A 198-41010-12 10-12 Ex. 9 Balance 2 0.10 30 G G 10-15 A G G G A 198-410 10-1510-15 Ex. 10 Balance 2 0.50 30 G G 10-15 A G G G A 198-410 10-15 10-15Ex. 11 Balance 2 1.00 50 G G 10-12 A G G G A 198-410 10-12 10-12 Ex. 12Balance 2 3.00 50 G G 10-12 A G G G A 198-410 10-12 10-12 Ex. 13 Balance10 0.02 30 G G 10-12 A G G G A 198-390 10-12 10-12 Ex. 14 Balance 100.05 30 G G 10-15 A G G G A 198-390 10-15 10-15 Ex. 15 Balance 10 0.1025 G G 15-20 A G G G A 198-390 15-20 15-20 Ex. 16 Balance 10 0.50 30 G G15-20 A G G G A 198-390 20-25 15-20 Ex. 17 Balance 10 1.00 50 G G 10-15A G G G A 198-390 20-25 10-15 Ex. 18 Balance 10 3.00 50 G G 10-15 A G GG A 198-390 20-25 10-15 Ex. 19 Balance 20 0.02 25 G G 10-15 A G G G A198-380 10-15 10-15 Ex. 20 Balance 20 0.05 25 G G 15-20 A G G G A198-380 15-20 15-20 Ex. 21 Balance 20 0.10 25 G G 20-25 A G G G A198-380 20-25 20-25 Ex. 22 Balance 20 0.50 25 G G 20-25 A G G G A198-380 20-25 20-25 Ex. 23 Balance 20 1.00 35 G G 20-25 A G G G A198-380 20-25 20-25 Ex. 24 Balance 20 3.00 35 G G 20-25 A G G G A198-380 20-25 20-25 Ex. 25 Balance 30 0.02 25 G G 10-15 A G G G A198-370 10-15 15-20 Ex. 26 Balance 30 0.05 25 G G 15-20 A G G G A198-370 15-20 20-25 Ex. 27 Balance 30 0.10 20 G G 20-25 A G G G A198-370 15-20 20-25 Ex. 28 Balance 30 0.50 20 G G 20-25 A G G G A198-370 20-25 20-25 Ex. 29 Balance 30 1.00 25 G G 15-20 A G G G A198-370 20-25 20-25 Ex. 30 Balance 30 3.00 25 G G 15-20 A G G G A198-370 20-25 20-25 Com. Ex. 3 100 — — 35 G P 1 — — — — — — 1 1 Com. Ex.4 — 100 — 10 G G <1 — — — — — — <1 <1

TABLE 3 Salt Spray Evaluation of the time period until red rust occurredHeat Immersion Immersion treatment in tap in sulfuric temperature wateracid Time range Time Time period in which the period period Degree ofuntil Addition amounts of corrosion until red until red white rust redrust Ti, Co, Ni and P prevention rust rust Components Hard- Workabilityoccurrence occurred (% by mass) effect was occurred occurred (% by mass)ness into [no heat [no heat [no heat treatment] improved [no heat [noheat Zn Sn Mg (Hv) wire treatment] treatment] 0.001 0.01 0.1 1 3 (° C.)treatment] treatment] Ex. 31 Balance 40 0.02 25 G G 10-12 A G G G A198-350 10-12 10-15 Ex. 32 Balance 40 0.05 25 G G 10-15 A G G G A198-350 10-15 15-20 Ex. 33 Balance 40 0.10 20 G G 15-20 A G G G A198-350 15-20 15-20 Ex. 34 Balance 40 0.50 25 G G 15-20 A G G G A198-350 15-20 15-20 Ex. 35 Balance 40 1.00 30 G G 10-15 A G G G A198-350 15-20 15-20 Ex. 36 Balance 40 3.00 30 G G 10-15 A G G G A198-350 15-20 15-20 Ex. 37 Balance 48 0.02 25 G G 10-12 A G G G A198-340 10-12 10-12 Ex. 38 Balance 48 0.05 25 G G 10-12 A G G G A198-340 10-12 10-12 Ex. 39 Balance 48 0.10 20 G G 10-15 A G G G A198-340 10-15 10-15 Ex. 40 Balance 48 0.50 20 G G 10-15 A G G G A198-340 10-15 10-15 Ex. 41 Balance 48 1.00 25 G G 10-12 A G G G A198-340 10-12 10-12 Ex. 42 Balance 48 3.00 25 G G 10-12 A G G G A198-340 10-12 10-12 Com. Ex. 5 Balance 1 0.10 35 G A 5-6 A G E G A198-410 5-6 4-5 Com. Ex. 6 Balance 2 0.01 35 G A 7-8 A G G G A 198-4107-8 7-8 Com. Ex. 7 Balance 2 5.00 130 P G 5-6 A G G G A 198-410 5-6 5-6Com. Ex. 8 Balance 10 0.01 30 G G  8-10 A G G G A 198-390  8-10  8-10Com. Ex. 9 Balance 10 5.00 120 P G 4-5 A G G G A 198-390 6-7 4-5 Com.Ex. 10 Balance 20 0.01 30 G G  8-10 A G G G A 198-380  8-10  8-10 Com.Ex. 11 Balance 20 5.00 100 P G 7-8 A G G G A 198-380 7-8 6-7 Com. Ex. 12Balance 30 0.01 30 G G  8-10 A G G G A 198-370  8-10  8-10 Com. Ex. 13Balance 30 5.00 70 P G 7-8 A G G G A 198-370 7-8 6-7 Com. Ex. 14 Balance40 0.01 30 G G  8-10 A G G G A 198-350  8-10  8-10 Com. Ex. 15 Balance40 5.00 70 P G 7-8 A G G G A 198-350 7-8 6-7 Com. Ex. 16 Balance 48 0.0125 G G 7-8 A G G G A 198-340 7-8 7-8 Com. Ex. 17 Balance 48 5.00 50 P G5-6 A G G G A 198-340 5-6 5-6 Com. Ex. 18 Balance 50 0.10 20 G G 7-8 A GG G A 198-340 7-8 7-8 Com. Ex. 3 100 — — 35 G P 1 — — — — — — 1 1 Com.Ex. 4 — 100 — 10 G G <1 — — — — — — <1 <1

In Examples 7 to 42 and Comparative Examples 5 to 18, when Ti, Co, Niand P were added each alone and the salt spray test was performed, thesame evaluation results were obtained, by varying the addition amount,on the time periods until red rust occurred. Therefore, also in Tables 2and 3 in the same manner as in Table 1, for simplicity, only one typicalexample is shown for each of Examples 7 to 42 and Comparative Examples 5to 18. Specifically, this means that in each of Examples 7 to 42 andComparative Examples 5 to 18, in any of the cases in which any one ofTi, Co, Ni and P was added, when the addition amount thereof was variedas 0.001, 0.01, 0.1, 1 and 3% by mass, the same results were obtainedfor all these elements as shown in Tables 2 and 3.

Examples 43 to 53

As shown in Table 4, in each of Examples 43 to 53, a Zn—Sn—Mg wire wasused as a first wire and a Zn wire was used as a second wire, andsimultaneously the first wire and the second wire were arc sprayed. Theresults thus obtained are shown in Table 4. In this tabularpresentation, in the same manner as in above-described Examples, in eachof Examples 43 to 53, when Ti, Co, Ni and P were added and the saltspray test was performed, in any of the cases in which any one of Ti,Co, Ni and P was singly added, the same evaluation results wereobtained, by varying the addition amount, on the time periods until redrust occurred. Therefore, also in Table 4, for simplicity, only onetypical example is shown for each of Examples 43 to 53.

TABLE 4 Components (% by mass) Zn Sn Mg Spray conditions Hardness (Hv)Workability into wire Ex. 43 Balance 2 0.02 Zn—4Sn—0.04Mg wire and Zn —— wire Ex. 44 Balance 2 3.00 Zn—4Sn—6.0Mg wire — — and Zn wire Ex. 45Balance 10 0.02 Zn—20Sn—0.04Mg — — wire and Zn wire Ex. 46 Balance 103.00 Zn—20Sn—6.0Mg wire — — and Zn wire Ex. 47 Balance 20 0.02Zn—40Sn—0.04Mg — — wire and Zn wire Ex. 48 Balance 20 3.00 Zn—40Sn—6.0Mgwire — — and Zn wire Ex. 49 Balance 30 0.02 Zn—60Sn—0.04Mg — — wire andZn wire Ex. 50 Balance 30 3.00 Zn—60Sn—6.0Mg wire — — and Zn wire Ex. 51Balance 40 0.02 Zn—80Sn—0.04Mg — — wire and Zn wire Ex. 52 Balance 403.00 Zn—80Sn—6.0Mg wire and Zn — — wire Ex. 53 Balance 48 0.02Zn—96Sn—0.4Mg wire and Zn — — wire Salt spray Evaluation of the timeperiod until red rust occurred Heat treatment temperature Immersion Timerange in in tap water Immersion in period which the Time period sulfuricacid Degree of until Addition amounts of corrosion until red Time periodwhite rust red rust Ti, Co, Ni and P prevention rust until red rustoccurrence occurred (% by mass) effect was occurred occurred [no [noheat [no heat [no heat treatment] improved [no heat heat treatment]treatment] 0.001 0.01 0.1 1 3 (° C.) treatment] treatment] Ex. 43 G12-14 A G G G A 198-410 12-14 12-14 Ex. 44 G 12-14 A G G G A 198-41012-14 12-14 Ex. 45 G 12-14 A G G G A 198-380 12-14 12-14 Ex. 46 G 15-20A G G G A 198-380 25-30 15-20 Ex. 47 G 15-20 A G G G A 198-350 15-2015-20 Ex. 48 G 25-30 A G G G A 198-350 25-30 25-30 Ex. 49 G 15-20 A G GG A 198-340 15-20 20-25 Ex. 50 G 20-25 A G G G A 198-340 25-30 25-30 Ex.51 G 12-14 A G G G A 198-290 12-14 15-20 Ex. 52 G 15-20 A G G G A198-290 20-25 20-25 Ex. 53 G 12-14 A G G G A 198-220 12-14 12-14

As can be seen from Table 1, in Examples 1 to 6 in each of which a Zn—Snalloy was sprayed, the used alloys were able to be wiredrawn withoutproblems and all the used alloys were able to yield a wire of 1.6 mm indiameter.

In each of Examples 1 to 6, the degree of white rust occurrence was lowand, additionally the time period until red rust occurred was long,hence sufficient corrosion prevention performance was attained. Becauseof the use of the Zn—Sn alloys, Examples 1 to 6 were free from problemsassociated with health. In each of Examples 1 to 6, the time perioduntil red rust occurred was approximately as excellent as the timeperiod concerned of the heretofore known Zn-15Al alloy. The cases whereat least any one of Ti, Co, Ni and P was added to the Zn—Sn alloy andthe cases where a heat treatment was applied after spraying were able tofurther improve the corrosion prevention property. With respect to theheat treatment, specifically, when the heat treatment was performed at atemperature falling in a range equal to or higher than the eutectictemperature, namely, 198° C., of the alloy forming the sprayed coatingand lower than the melting point of the alloy sprayed coating, thecorrosion prevention effect was able to be improved by a heat treatmentfor 30 minutes; the corrosion prevention property when immersion in tapwater was made and the corrosion prevention property when the immersionin sulfuric acid was made were also excellent.

On the contrary, in Comparative Example 1, the mixing proportion of Snwas lower than the range of the present invention, hence the mixingproportion of Zn was correspondingly higher, and accordinglycorresponding white rust occurrence was observed. Because the mixingproportion of Sn was lower than the range of the present invention, Snhardly displayed the function of suppressing the elution of Zn, andhence the time period until red rust occurred was extremely shorter ascompared to Examples 1 to 6.

In Comparative Example 2, the mixing proportion of Sn was, in contrast,larger than the range of the present invention, but the time perioduntil red rust occurred was similarly shorter as compared to Examples 1to 6.

In Comparative Example 3, only Zn was sprayed, and hence the degree ofwhite rust occurrence was further higher and the time period until redrust occurred was also shorter as compared to Comparative Example 1.

In Comparative Example 4, only Sn was sprayed, and hence the time perioduntil red rust occurred was further shorter as compared to ComparativeExample 2.

As can be seen from Tables 2 and 3, in Examples 7 to 42 in each of whicha Zn—Sn—Mg alloy was sprayed, the used alloys were able to be wiredrawnwithout problems and all the used alloys were each able to yield a wireof 1.6 mm in diameter.

In each of Examples 7 to 42, the degree of white rust occurrence was lowand, additionally the time period until red rust occurred was long,hence sufficient corrosion prevention performance was attained. In eachof Examples 7 to 42, the time period until red rust occurred wasapproximately as excellent as or more excellent than the time periodconcerned of the known Zn-15Al alloy. The cases where at least any oneof Ti, Co, Ni and P was added to the Zn—Sn—Mg alloy and the cases wherea heat treatment was applied after spraying were able to further improvethe corrosion prevention property. With respect to the heat treatment,specifically, when the heat treatment was performed at a temperaturefalling in a range equal to or higher than the eutectic temperature,namely, 198° C., of the alloy forming the sprayed coating and lower thanthe melting point of the alloy sprayed coating, the corrosion preventioneffect was able to be improved by a heat treatment for 30 minutes; thecorrosion prevention property when immersion in tap water was made andthe corrosion prevention property when the immersion in sulfuric acidwas made were also excellent.

On the contrary, in Comparative Example 5, as shown in Table 3, themixing proportion of Mg offered no problem; however, the mixingproportion of Sn was lower than the range of the present invention,hence the mixing proportion of Zn was correspondingly higher andaccordingly corresponding white rust occurrence was found. Additionally,the time period until red rust occurred was shorter as compared toExamples 7 to 42.

In each of Comparative Examples 6, 8, 10, 12, 14 and 16, the mixingproportion of Sn offered no problem; however, the mixing proportion ofMg was lower than the range of the present invention, Mg hardlydisplayed the function of suppressing the elution of Zn, and hence thetime period until red rust occurred was shorter as compared to Examples7 to 12, 13 to 18, 19 to 24, 25 to 30, 31 to 36 and 37 to 42.

In Comparative Examples 6, 8, 10, 12, 14 and 16 as compared respectivelyto Examples 1, 2, 3, 4, 5 and 6, which were respectively the same in themixing proportions of Zn and Sn as these Comparative Examples, althougha slight amount of Mg was added, the time period until red rust occurredwas made rather shorter. The reasons for this fact are not clear;probably, the addition amount of Mg was very small, and hence no effectof the addition of Mg was manifested, and some factors leading to poorresults functioned.

In each of Comparative Examples 7, 9, 11, 13, 15 and 17, the mixingproportion of Sn offered no problem; however, the mixing proportion ofMg was higher than the range of the present invention, and hence thecorrosion prevention property was extremely degraded. Consequently, redrust occurred in an extremely short time period as compared to Examples7 to 42.

In Comparative Example 18, the mixing proportion of Mg offered noproblem; however, the mixing proportion of Sn was higher than the rangeof the present invention, and hence the time period until red rustoccurred was shorter as compared to Examples 7 to 42.

In Examples 43, 44, 45, 46, 47, 48, 49 and 50, for the purpose ofobtaining the coatings having the same compositions as the compositionsrespectively in Examples 7, 12, 13, 18, 19, 24, 25 and 30, the Zn—Sn—Mgwires each having a doubled amount of Sn and a doubled amount of Mg inrelation to the corresponding Example and the Zn wire including only Znwere used. Consequently, it was verified that in any of Examples 43 to50, as compared to the corresponding Examples 7, 12, 13, 18, 19, 24, 25and 30, the time period until red rust occurred due to the immersion intap water and the time period until red rust occurred due to theimmersion in sulfuric acid were longer, hence the corrosion preventionperformance was further improved.

Also in each of Examples 51 to 53, in the same manner as in Examples 43to 50, the time period until red rust occurred due to the immersion intap water and the time period until red rust occurred due to theimmersion in sulfuric acid were both long, hence the corrosionprevention performance was excellent.

Although no description is made in Tables 1 to 4, in the case where tothe Zn—Sn alloy or the Zn—Sn—Mg alloy, at least any one of Ti, Co, Niand P was added, and after spraying, a heat treatment was performed at atemperature falling in a range equal to or higher than the eutectictemperature, namely, 198° C., of the alloy forming the sprayed coatingand lower than the melting point of the alloy sprayed coating, thecorrosion prevention property was able to be further improved.

Example 54

Hereinafter, an example of the process for production of an alloy wireof the present invention is described.

By using an apparatus shown in FIG. 1, under the below-describedconditions, an alloy wire 105 in which crystals were refined, theductility thereof was improved and the diameter thereof was 10 mm wasobtained. Then, the alloy wire 105 was worked into an alloy wire havinga diameter of 1.6 mm with a not-shown wiredrawing machine.

Specifically, in the above-described production process, the timing ofspraying cooling water was altered and quenching was performed. Morespecifically, as shown in Table 5, the timing of spraying cooling water(hereinafter, referred to as “water cooling timing”) was varied, andthus the specimens 1 to 4 were produced.

In other words, Zn, Sn and Mg were melted at 450° C., and these moltenmaterials were mixed in such a way that the content of Sn was 30% bymass, the content of Mg was 0.3% by mass and the balance was composed ofZn to yield a molten alloy. With reference to the timing (hereinafter,referred to as “arrival timing”) at which the molten alloy 103discharged from the molten alloy outlet 116 of the crucible 115 shown inFIG. 1 arrived at the groove 112, the water cooling timing was varied.Specifically, the position of the spray nozzle 113 shown in FIG. 1 wasadjusted along the rotation direction of the casting wheel 111 so as togive a required water cooling timing.

Each of the obtained specimens 1 to 4 was subjected to a tensile test tomeasure the tensile strength and the elongation, also subjected to abending test to measure the load and the breaking angle, and subjectedto a measurement of the Vickers hardness Hy; the average values over thevalues obtained by six times repeated measurements were adopted as themeasurement results.

The bending test was performed according to JIS Z 2248 “Bending testmethod for metal material.” Specifically, as shown in FIG. 2, thespecimen 150 having a diameter of 1.6 mm was made to take a positionwith the axis direction thereof to be horizontal and was placed, on apair of supports 161 and 162 each having a diameter of 10 mm and beingdisposed at a certain horizontal interval, so as to bridge over thispair. A pushing metal rod 163 having an end cross-sectional shape of asemicircle of 5 mm in radius vertically applied a load 170 to thespecimen 150 at a position between the support 161 and the support 162.

Thus, as shown in FIG. 2, the specimen 150 was deformed into a V-shape.At the time of the breaking of the specimen 150 due to the deformation,the bending angle θ was measured, wherein the bending angle θ was anangle formed by the crossing of the extended line of the portion 151 ofthe specimen 150 in contact with one of the supports, namely, thesupport 161 and the extended line of the portion 152 of the specimen 150in contact with the other of the supports, namely, the support 162. Itis to be noted that the bending angle θ was an angle while the load 170was being applied, but not the angle after the load was removed. At thistime, the occurrence and nonoccurrence of cracks, flaws and otherdefects in the curved outer portion of the curved portion 153 of thespecimen 150 were examined.

(Specimen 1)

An alloy wire produced under the conditions without water cooling wasadopted as the specimen 1. In the specimen 1, the tensile strength was125 N/mm² and the elongation was 1%; and when the bending test wasperformed, the specimen 1 was broken under a load of 20 N and at abending angle θ of 40 degrees. The Vickers hardness Hv was found to be26.

The evaluation results for the specimen 1 are shown in Table 5.

TABLE 5 Temperature Application or non- (° C.) Tensile test Bending testapplication of water Before After Tensile Breaking cooling (Water waterwater strength Elongation Load angle Hardness Specimen cooling timing)cooling cooling (N/mm²) (%) (N) (degrees) (Hv) 1 Not applied — — 125 120 40 26 2 Applied (30 seconds 200-250 20-40 154 10 25 150 35 afterdischarge of molten alloy) 3 Applied (15 seconds 250-300 30-50 150 14 25No breaking 35 after discharge of at 180° molten alloy) 4 Applied (5seconds 300-350 30-50 155 16 25 No breaking 35 after discharge of at180° molten alloy)

(Specimen 2)

An alloy wire produced under the conditions with water cooling wasadopted as the specimen 2. The water cooling timing was set at 30seconds after the arrival timing of the molten alloy 103 at the groove112 shown in FIG. 1. In the cooling, cooling water at normal temperaturewas continuously sprayed for 5 to 10 seconds. The temperature of themolten alloy 104 before the water cooling was 200 to 250° C., and thetemperature of the wire 105 after the water cooling was 20 to 40° C. Inthe specimen 2, the tensile strength was 154 N/mm² and the elongationwas 10%; and when the bending test was performed, the specimen 2 wasbroken under a load of 25 N and at a bending angle θ of 150 degrees. TheVickers hardness Hv was found to be 35.

The evaluation results for the specimen 2 are shown in Table 5.

(Specimen 3)

An alloy wire produced under the conditions with water cooling wasadopted as the specimen 3. The water cooling timing was set at 15seconds after the above-described arrival timing. In the cooling,cooling water at normal temperature was continuously sprayed for 5 toseconds. The temperature of the molten alloy 104 before the watercooling was 250 to 300° C., and the temperature of the wire 105 afterthe water cooling was 30 to 50° C. In the specimen 3, the tensilestrength was 150 N/mm² and the elongation was 14%; and the bending testwas performed, and consequently the specimen 3 was not broken under aload of 25 N and even at a bending angle θ of 180 degrees. The Vickershardness Hv was found to be 35.

The evaluation results for the specimen 3 are shown in Table 5.

(Specimen 4)

An alloy wire produced under the conditions with water cooling wasadopted as the specimen 4. The water cooling timing was set at 5 secondsafter the arrival timing. In the cooling, cooling water at normaltemperature was continuously sprayed for 5 to 10 seconds. Thetemperature of the molten alloy 104 before the water cooling was 300 to350° C., and the temperature of the wire 105 after the water cooling was30 to 50° C. In the specimen 4, the tensile strength was 155 N/mm² andthe elongation was 16%; and the bending test was performed, andconsequently the specimen 4 was not broken under a load of 25 N and evenat a bending angle θ of 180 degrees. The Vickers hardness Hv was foundto be 35.

The evaluation results for the specimen 4 are shown in Table 5.

In addition to these measurements, a microstructure observation was alsoperformed. FIG. 3 shows a result of an optical microscope observation ofthe microstructure of the specimen 1 produced under the conditionswithout water cooling. As shown in the figure, a dendriticmicrostructure generated by the dendritic precipitation of the zinccrystals was observed. In FIG. 3, black portions represent zinc crystalsand the white portions represent the eutectic crystals.

FIG. 4 shows a result of an optical microscope observation of themicrostructure of the specimen 4 produced under the conditions withwater cooling. As shown in the figure, an acicular microstructuregenerated by the acicular precipitation of the zinc crystals wasobserved. Further, the zinc crystals were finer as compared to the alloywire of FIG. 3 produced under the conditions without water cooling.

As described above, when quenching was performed by spraying coolingwater, the mechanical properties of the alloy wire were improved.Further, the earlier was the timing of the cooling water spraying, thebetter results were obtained. Specifically, as is clear from themeasurement results of the tensile test, the specimens 2 to 4 producedunder the conditions with water cooling were improved in tensilestrength by about 20% and drastically improved in elongation as comparedto the specimen 1 produced under the conditions without water cooling.Additionally, the specimens 2 to 4 produced under the conditions withwater cooling were shown to be hardly broken, from the measurementresults of the bending test, and the specimens 2 to 4 each showed a highVickers hardness value.

Among the alloy wires produced in the similar manner under theconditions with water cooling, the specimen 3 for which the timing ofthe cooling water spraying was earlier than for the specimen 2 was morehardly broken than the specimen 2; the specimen 4 for which the timingof the cooling water spraying was earlier than for the specimen 3 waslarger in elongation than the specimen 3.

Consequently, as described above, in the working of an alloy wire havinga diameter of 10 mm into an alloy wire having a diameter of 1.6 mm witha wiredrawing machine, the occurrence of the wire breaking was observedwhen the specimen 1 produced under the conditions without water coolingwas obtained, but no wire breaking occurred when the specimens 2 to 4produced under the conditions with water cooling were obtained.

As described above, the production under the conditions with watercooling enabled to refine the zinc crystals and enabled to improve themechanical properties of the alloy wire. Further, the adoption of theearlier timing of the cooling water spraying enabled to promote therefinement of the zinc crystals and to improve, in particular, theductility.

Having described the invention, the following is claimed:
 1. A Zn—Sn—Mgalloy for spraying comprising Sn in a content of more than 1% by massand less than 50% by mass, Mg in a content of more than 0.01% by massand less than 5% by mass and a balance composed of Zn.
 2. The Zn—Sn—Mgalloy for spraying according to claim 1, said alloy further comprisingat least any one of Ti, Co, Ni and P, wherein a content of each of Ti,Co, Ni and P is more than 0.001% by mass and less than 3% by mass.
 3. Analloy wire composed of the Zn—Sn—Mg alloy for spraying according toclaim
 1. 4. An alloy wire composed of the Zn—Sn—Mg alloy for sprayingaccording to claim 2.